The present invention relates to hazardous duty garments and, more particularly, to lightweight firefighter garments which protect a wearer from extreme ambient conditions.
Protective garments are designed to shield a wearer from a variety of environmental hazards, and firefighter garments are representative of such garments. A conventional firefighting ensemble comprises a turnout coat and pant, each of which includes an outer shell, a moisture barrier located within the outer shell, a thermal liner located within the moisture barrier and an innermost face cloth layer. The outer shell typically is constructed of an abrasion-, flame- and heat-resistant material such as a woven aramid material, typically NOMEX or KEVLAR (both are trademarks of E.I. DuPont de Nemours & Co., Inc.) or a polybenzamidazole such a PBI (a trademark of Celanese Corp.) fiber material. The moisture barrier typically includes a semipermeable membrane layer which is moisture vapor permeable but impermeable to liquid moisture, such as CROSSTECH (a trademark of W.L. Gore & Associates, Inc.). The membrane layer is bonded to a substrate of flame- and heat-resistant material, such as an aramid or PBI material.
The thermal liner is typically positioned within the moisture barrier in order to prevent the thermal liner from soaking up liquid moisture flowing through the outer shell from the ambient. The thermal liner typically comprises a layer of insulation material, such as a relatively thick layer of aramid fiber batting or needlepunch, which is often quilted to a lightweight aramid fabric substrate or face cloth. The batting of the thermal barrier traps air and possesses sufficient loft to provide the necessary thermal resistance, and the fabric substrate protects the batting of the thermal liner from abrasion from the wearer.
The aforementioned components typically are arranged within the garment so that the moisture barrier layer is positioned between the thermal liner and the outer shell. This is necessary to prevent the insulating material of the thermal liner from absorbing an excessive amount of liquid moisture from the ambient, which increases the overall weight of the garment and reduces breathability of the thermal liner, thereby increasing the stress imposed by the garment on the wearer, and reduces its loft and thermal resistance characteristics. However, one disadvantage with such an arrangement is that the laminated membrane of the moisture barrier is relatively delicate and can be damaged by heat, abrasion or puncture. Such damage results in increased exposure of the thermal liner to liquid moisture, which increases liquid moisture absorption.
Another disadvantage inherent in such an arrangement is that the moisture barrier layer adds to the bulk and weight of the garment and inhibits freedom of movement of the wearer, producing a "hobbling effect," increasing the stress imposed on the wearer in situations requiring high activity, and accelerates the onset of fatigue. Furthermore, with such an ensemble some perspiration moisture vapor from the wearer is absorbed by the thermal liner. Moreover, the combination of a discrete moisture barrier and thermal liner limits breathability, especially if the thermal liner is positioned within the moisture barrier.
Additionally, many conventional firefighting garments are designed such that their thermal liner, while positioned within the moisture barrier, actually promotes the absorption of fluids, such as a firefighter's perspiration. While such a garment may provide the firefighter short term comfort by keeping the firefighter's skin relatively dry, in the long term, such a thermal liner will tend to lose its insulating characteristics (much like a wet pot-holder) because moisture conducts heat energy better than air.
Accordingly, there is a need for a protective garment in which the susceptibility of the thermal liner to absorption of perspiration moisture and other moisture is minimized; a protective garment which is relatively thin and lightweight, yet provides adequate thermal protection; a protective garment which is inherently able to withstand a temperature of 500.degree. F. for at least five minutes without igniting, melting or dripping, making it suitable for use as a firefighting garment; and a protective garment which minimizes the restriction of movement and hobbling effect characteristic of conventional firefighting garments.